Brush holder assembly



Aug. 13, 1957 M. A. BAKER BRUSH HOLDER ASSEMBLY Filed Sept. 23, 1955 I IIIIIHI l'] [27 van far"; Marv/i7 /4 Bea/re);

HA; Attorney United States Patent BRUSH HOLDER ASSEMBLY Marvin A. Baker,Erie, Pa., assignor to General Electric Company, a corporation of NewYork Application September 23, 1955, Serial No. 536,089

17 Claims. (Cl. 310-246) This invention relates to dynamo-electricalmachinery and more particularly to brush assemblies for use onelectrical motors and generators.

The use of a coiled compression spring for maintaining motor andgenerator brush contact is known in the art. Previously, brush holdersincorporating coiled compression springs which are pre-stressed prior toassembly and have one end attached to fixed members with the distal endsterminating in a spiral coil adapted to engage the outer ends of thebrushes have been suggested. This type of spring has been acceptable dueto its inherent property of exerting a force on brushes which issubstantially constant throughout the (life of brushes, even though thebrushes are long when installed and their length is decreased by wearuntil they are worn extremely short.

This type of spring as heretofore applied to brushes of the typediscussed may apply a force to the brush in a manner which may cause thebrush to be drawn away from the brush holder reaction surface by theforce of the commutator thereon. The effect of the movement of the brushaway from the reaction surface may result in brush chatter, sparking atthe commutator, or rapid brush wear.

One feature of the present disclosure is a constant tension spring whichapplies a force to the brush at a point spaced from and on the side ofthe central axis of the brush remote from the reaction surface with theforce having a sense inclined toward the commutator and toward thereaction surface. The resultant of the force applied by the spring andthe frictional force of the rotating commutator on the opposite end ofthe brush produces a wedging action which holds the brush firmly againstthe reaction surface in either direction of rotation, thus inhibitingany tendency of the brush to chatter with the inherent undesirableresults.

Furthermore, when springs are applied to brushes in the manner old inthe art as aforesaid, the end engaging the brush has a tendency to creepacross the surface of the end of the brush toward the reaction surfaceas the volute rolls up, until it reaches a point Where it will slip. Asit slipped, it would tend to pull the brush with it away from thereaction surface.

To overcome the tendency of the volute to creep over the surface of thebrush, this invention discloses a restraining surface on the brush forengaging the spring. This surface may take the form of a flanged plateattached to the brush as disclosed in one embodiment or it may be anotch properly located to receive the brush end as disclosed in anotherembodiment herein. According to this invention, the restraining meanscould be any form of stop for the spring.

Under conditions of severe shock, brushesv may jump out of the holder.,To overcome. this tendency and to prevent the brushes from jumping outof the holder, a keeper isv disclosed. The keeper also preventsvnegligent operators from; over-stressing the. spring when replacingbrushes, etc.

2,802,960 Patented Aug. 13, 1957 Another important feature of thepresent invention is an improved shape of spring which insures properuniform pressure and force sense as the brush wears and, consequently,the brush helix re-rolls itself with the resulting tendency not to loseits tension. This action may be facilitated by an improved brushmounting disclosed herein as Well as by a reinforcing element shown incombination with the spring.

Still another feature is a guard or keeper disposed parallel to thespring with a portion overlying the brush to keep the spring fromjumping out and to protect the spring.

With the above and other advantages in view, the present inventionconsists of the combination and arrangement of parts hereinafter morefully described, illustrated in the accompanying drawing and moreparticularly pointed out in the appended claims, it being understoodthat changes may be made in the form, size, proportions, and minordetail of construction without departing from the spirit or sacrificingany of the advantages of the invention.

In the drawing:

Fig. 1 is a side elevational view partly in section of the improvedbrush holder and coiled spring assembly of this invention showing thereaction surface engaged by the brush;

Fig. 2 is a top view of the assembly shown in Fig. 1;

Fig. 3 is a side elevational view similar to Fig. 1 showing anotherembodiment of the invention;

Fig. 4 is a view similar to Figs. 1 and 2 of still another embodiment ofthe invention;

Fig. 5 is still another view similar to Figs. 1, 3 and 4 showing anotherembodiment of the invention; and

Fig. 6 shows another embodiment of the invention.

Referring now to the embodiment of the invention shown in Figs. 1 and 2,the commutator of a dynamoelectric machine such as a motor or generatoris shown at 10. The longitudinal axis of a brush 12 is disposedgenerally parallel to the vertical center line of the commutator 10 andspaced on the leading side therefrom. The brush 12 will be provided withthe usual pigtail or other suitable electrical connection to connect thebrush 12 to a suitable electrical terminal conductor.

A brush casing 11 has ends 17 and 18 connected by side members 19 whichjoin the end members 17 land 18 together and are also joined to a bottom21. The bottom 21 has an opening 22 therethrough adjacent the reactionsurface to receive the lower end 23 of the brush 12. A commutatorengaging surface 24 of the brush 12 will be formed in a general contourto conform to the peripheral surface of the commutator 10. The upper end26 of the brush 12 is relieved at 27 and an outer plate 28 extends overthe upper surface and bends over the outer leading edge corner and isattached thereto. The upper end 26 of the brush 12 terminates in asurface 30 preferably inclined at an angle to the transverse axis of thebrush 12.

The plate 28 is attached to the upper end of the brush 12 by a suitablemeans. A flange 32 is attached to the plate 23 at an intermediate pointthereon and extends upwardly therefrom generally perpendicular thereto.

A bracket is integrally attached to the brush casing 11 and has -a bore41 which receives a stud 42. The stud 42 is rigidly attached to thefixed frame of the machine and insulated therefrom. The bracket 40 has aslot. 43 cut therein which has a continuation 44 on the opposite side ofthe bore 41. A bolt 45 threa-dably engages the end of the bracket 40,clamping the bracket 40 to the stud 42 in the usual manner. This makesit possible to loosen the bolt 45 and thereby rotate the bracket 40 onthe stud 42 to bring the brush 12 into alignment with respect to thecommutator and, at the same time, the bracket 40 may be slid along thestud 42 to properly locate the brush 12 relatively to the axis of thecommutator 10.

A spring 14 is substantially a constant pressure spring and is made of amaterial flat in cross section and prestressed along its length so as tonaturally assume a free self-winding volute coil 15 of a diameter whichwill nest well into the space between the flange 32 and the end 63 ofthe plate 28. The spring 14 is attached to the inner surface 74 of theend 18 and is attached thereto by means of rivets 16; however, it couldbe attached by any other suitable fastening means. The spring 14 is benttoward the brush 12 at 75 and the force on the coil 15 puts an inversebend in the spring 14 as shown. As the commutator 10 rotates and wearsaway the lower end 23 of the brush 12, the brush 12 will be urgeddownward by the force of the coil 15 on the top of the plate 28 and, atthe same time, the upper end of the brush 12 will be urged toward thereaction surface 29. The lower end of the brush 12 will be urged towardthe reaction surface 29 by reason of the frictional force on the lowersurface thereof by rotation of the commutator 10. Therefore, the brush12 will be bodily moved toward the reaction surface 29 and held in firmrelation thereagainst. As the brush 12 wears away and shortens, thevolute coil 15 will rewind and the frictional force of the portionthereof engaging the plate 28 will tend to cause the volute to climbtoward the reaction surface 29. This tendency will be opposed by theflange 32 which will hold it in the position shown throughout the lifeof the brush 12, thereby causing the spring 14 to exert a resultantforce on the outer end of the brush 12 which will do its part in holdingthe outer end in firm engagement with the reaction surface 29.

In order to obtain the optimum pressure on the brush 12 toward thereaction surface 29, a leaf spring 72 may be used. The use of such aspring is made possible by the positive stops provided which consist ofthe flange 32. The leaf spring 72 is attached to the brush casing 11 bythe rivets 16 or other suitable means and is disposed between the spring14 and the casing 11. The leaf spring 72 may be bent to pre-stress it toexert the optimum pressure on the brush 12 toward the reaction surface29.

In the embodiment of the invention shown in Fig. 3, a spring and brushassembly is shown in some respects similar to that shown in Fig. 1. Thecorresponding parts in Fig. 3 to the corresponding parts in Fig. l aresometimes numbered with the same number having one hundred added theretoto distinguish between the two embodiments. Fig. 3 shows a brush casing111 supporting a brush 112. The brush casing 111 has end 117 and aspring supporting reaction end 118 and sides 119. Brush surface 124engages the outer periphery of a commutator 110. A constant pressurespring 114 having a volute end 115 is attached to the inner surface 144of the end 118. The surface 144 tapers outwardly and toward the brush112, thereby causing the spring 114 to incline toward the brush 112. Akeeper 150 is attached to the surface 144 between the spring 114 and thesurface by means of rivet 116 and rivet 116 passes through both thekeeper 150 and the spring 114. The spring 114 could be attached to thesurface 144 by other suitable means than the rivet 116.

A slot 133 is formed in the outer end 126 of the brush 112 at the sidethereof remote from reaction surface 129 and the side portion thereof isnested in the slot 133. As wear reduces the length of the brush 112, thevolute 115 winds itself up and the edge 132, as well as the inclinededge 130, holds the volute 115 in positive relationship with the brush112 and insures a resultant force applied by the spring 114 in adirection to force the brush 112 downward in opening 122 as well astoward the reaction surface 129 so that the resultant force applied tothe brush 112 by means of the spring 114, when combined with thefrictional force of the rotating commutator on the lower end of thebrush 112, holds the brush 112 firmly against the reaction surface 129.

In the embodiment of the invention shown in Fig. 4, a brush casing 211is disclosed having a reaction end 217, spring end 218, sides 219, and abottom 221. The bottom 221 has an opening 222 therethrough. Thecommutator end 223 of brush 212 extends through the opening 222 and thecommutator end surface 224 of the brush 212 engages the peripheralsurface of the commutator 210. The brush casing 211 has the sides 219which connect the ends and bottom 221 together.

Upper surface 230 of the brush 212 has a plate 228 thereon which bendsover at 227 into a relief therein whereby it is firmly fixed to thebrush 212. The opposite end of the plate 228 from the end 227 has avolute receiving saddle 1230. A constant pressure spring 214 is attachedat its lower end by means of rivet 216 or other suitable means to theinner face of spring support end 218 and is supported against the spacer260 which is disposed between a keeper or backing member 250 and thelower end of the spring 214. The spring 214 is bent at 245 toward thebrush 212 whereby the spring 214, when urged to the stressed positionshown, exerts a force downward and toward reaction surface 229.

The keeper 250 serves the dual purpose of forming a guard to prevent thespring 214 from coming out of place during disassembly and also forms aconvenient means for holding the spring 214 in place while the rivet 216is put into position.

It will be noted that as the brush 212 wears away and shortens, volute215 will reroll but will be held in position nested in the saddle 1230whereby a resultant force will be exerted on the brush 212 toward thecommutator 210 and toward the reaction surface 229. This resultantforce, in combination with the frictional force between the commutator210 and the surface 224, will urge the brush 212 bodily toward thereaction surface 229, thereby holding it in position.

The embodiment of the invention shown in Fig. 5 discloses a brush casing311 which has ends 317 and 318 connected by sides 319 and having abottom portion 321. The outer peripheral surface of commutator 310 isengaged by conforming surface 324 of lower end 323 of a brush 312. Theupper surface 330 of the brush 312 is inclined downwardly at an angle A.It has been discovered that the angle A must be between twenty-fivedegrees and forty-five degrees. If the angle is greater than forty-fivedegrees, the effective length of the brush is reduced since the beveledsurface takes up an appreciable percentage of the length and thusshortens its life. If it is less than twenty-five degrees, the forcetoward the reaction surface will not be sufficient for desirable resultsand the volute will tend to slip on the upper end surface of the brushwith the resulting undesirable effects.

The volute 315 of the spring 314 engages the surface and, due to thelarge angle of the surface 330, the brush volute 315 will be restrainedagainst its natural inclination to climb upward on the surface 330 asthe brush 312 shortens due to wear and the volute 315, therefore,rerolls.

The brush 312 is attached to the inner surface 344 of the end 318 bymeans of a rivet 316 or other suitable means which extends through thelower end 325 of the constant pressure spring 314 and through a keeper350. The spring 314 is bent at 345 toward the brush 312. The keeper 350protects the spring 314 against damage and also provides a means forpreventing the brush 312 from jumping out of its casing 311 in case ofshock due to explosion on shipboardand due to similar shocks.

During operation, the commutator 310 preferably rotatesin thedirectionindicated and the frictional force on the surface 324, when combinedwith the resultant force of the volute 315 toward the reaction' surface329,

holds the brush 312 against the reaction surface 329 in positiverelation thereto.

In the embodiment of the invention shown in Fig. 6, a brush 412 issupported in a brush holder 411 and rests against the reaction surface429. The lower end of the brush holder 411 at 417 engages the surface422 of the brush 412. The inner end surface 424 of the brush 412 engagesthe outer peripheral surface of commutator 410. A spring 414 is attachedto the brush holder 411 at 475 and terminates at the upper end thereofin a tightly wound volute 415 which engages the upper tapered surface463 of the brush 412 and engages the flange or pin 430 at 432. Theflange or pin 430 could be molded into the brush 412 or tamped orpressed thereinto. The flange 430 restrains the brush 412 againstmovement over the end of the brush 412 toward the reaction surface 429and, therefore, provides a positive stop.

An auxiliary spring 470 is fastened to the brush holder 411 at 474 andthe upper end 472 engages the volute 415 at 471, exerting an additionalforce toward the flange 430 which adds to the force in that directionexerted by the volute 415 and urges the brush 412 toward the reactionsurface 429. The tension on the spring 470 can be adjusted to obtain theoptimum force toward the flange 434) and, because of the flange or pin430, a positive stop is provided to prevent the volute 415 from climbingup the brush 412.

The foregoing specification sets forth the invention in a practical formbut the structure shown is capable of modification within a range ofequivalents without departing from the invention which is to beunderstood is broadly novel as is commensurate with the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A commutator brush holder comprising a brush casing, and an elongatedspring, the commutator end of said spring being attached to said casingand the distal end of said spring terminating in a self-winding volutearranged to engage the upper end of a brush in said casing, said casinghaving an opening therethrough with a reaction surface on the insideedge thereof, one end of said brush being adapted to engage acommutator, the other end of said brush having a stop member afiixedthereon to restrain said volute against movement toward said reactionsurface, said spring being adapted to apply a force to said brush tourge said brush toward said reaction surface and toward said commutatoradapted to be engaged by the commutator end of said brush.

2. The brush holder recited in claim 1 wherein said means to restrainmovement of said volute comprises a flange attached to said brushinwardly from the edge adjacent said spring, said volute engaging saidmeans including said flange.

3. The brush holder recited in claim 1 wherein said i means to restrainmovement of said volute comprises a plate attached to the end surface ofsaid brush remote from said commutator end and extending outwardtherefrom, said end surface being inclined toward said spring, saidplate extending outwardly beyond the edge of said brush adjacent saidspring, and means on said plate to restrain said volute against movementover said plate toward said reaction surface.

4. The brush holder recited in claim 3 wherein said plate has a flangeattached thereto intermediate the ends thereof, said volute of saidspring being disposed against the overhanging ends of said plate andsaid flange.

5. In combination, a dynamo-electric machine having a commutator and abrush holder comprising a brush casing having a spring engaging end anda reaction surface portion, an opening through said casing, one insideedge of said opening comprising a reaction surface, means to attach saidbrush holder to a fixed member adjacent the commutator on saiddynamo-electric machine, an elongated brush adapted to extend throughsaid opening engagement with an inner surface of said reaction surface,the commutator end of said brush being disposed outside said casing andthe end of said brush opposite said commutator end being inclined towardsaid commutator end and away from said-inside surface, a plate attachedto and lying along said end of said brush opposite said commutator end,said plate overhanging said brush remote from said reaction surface, theother end of said plate extending into a notch in said brush, and a flatelongated spring having one end coiled into a self-winding voluteengaging said plate and a flange, the other end of said spring beingattached to said brush holder, said spring being adapted to urge saidbrush into engagement with said reaction surface, said brush beingdisplaced from the transverse center line of said commutator parallelthereto on the side thereof toward said reaction surface.

6. The combination recited in claim-5 wherein said casing has two sidesand a bottom attached to said sides and end, said opening beingformed'in said bottom on the side thereof adjacent said reactionsurface, said spring being attached to said brush holder at a pointspaced from said brush.

7. A brush holder for a dynamo-electric machine having a commutatorcomprising a brush casing having a spring supporting end and a reactionsurface end, a bottom on the commutator end of said brush holder, anopening in said bottom adjacent said reaction surface end, an elongatedbrush disposed in said opening and lying along said reaction surface, anelongated spring attached to said spring supporting end and extendingtherefrom, the distal end of said spring being in the form of aself-winding volute, and a notch formed in said brush in the upperportion thereof where the side remote from said reaction surface engagesthe end remote from said commutator end, said volute being disposed insaid notch and adapted to urge said brush toward said reaction surfaceand toward said commutator.

8. The brush holder recited in claim 7 wherein said spring supportingend has a surface adjacent said brush inclined away from said commutatorand toward said brush, said spring attached to said spring supportingsurface having its attached end inclined upwardly and toward said brush.

9. The brush holder recited in claim 8 wherein an elongated handle isattached to said inclined spring supporting surface between said springand terminating in a hook member overlying said volute.

10. In combination, a dynamo-electric machine having a commutator and abrush holder attached thereto comprising a brush casing having a springsupporting end and a reaction surface end, a bottom on the commutatorend of said reaction surface end, an opening in said bottom, anelongated brush disposed in said opening and lying along said reactionsurface, an elongated spring attached :to said spring supporting end andextending therefrom, a distal end of said spring being in the form of aself-winding volute, a notch formed in said brush in the corner thereofwhere the side remote from said reaction surface engages the end remotefrom said commutator end, said volute being disposed in said notch andadapted to urge said brush toward said reaction surface and toward saidcommutator, said spring supporting end having a surface adjacent saidbrush inclined away from said commutator and toward said brush, saidspring attached 10 said spring supporting surface having its at tachedend parallel to said inclined surface, and an elongated handle attachedto said inclined surface between said spring and said surface, saidhandle extending along said spring and terminating in a hook memberoverlying said volute, said brush being displaced from the center lineof said commutator in a direction toward said reaction surface.

11. A commutator brush holder comprising a brush casing, an elongatedspring in said casing, the commuta- 7 tor end of said spring beingattached to said casing and the distal end of said spring terminating ina self-winding volute, said casing having an opening therethrough with areaction surface On the inside edge thereof, and a brush adapted toengage a commutator, the other end of said brush having means thereon torestrain said volute against movement toward said reaction surface, saidmeans comprising a plate attached to the end of said brush remote fromsaid commutator, said plate overhanging the edge of said brush adjacentsaid spring and said plate having a concave surface :there-on, saidvolute of said spring engaging said concave surface whereby said springurges said brush toward said commutator and toward said reactionsurface.

12. The brush holder recited in claim 11 wherein said brush is offsetfrom the center line of said commutator on the side thereof toward saidreaction surface.

13. The brush holder recited in claim 12 wherein said spring is attachedto said brush casing by means on the inside of one end surface of saidcasing, and a keeper extends co-extensive with said spring and upwardlytherefrom and terminates in a curved portion overlying the volute ofsaid spring disposed thereon with a spacer between said spring and saidkeeper.

14. In combination, a dynamo-electric machine having a commutator and abrush holder attached to said machine adjacent said commutator, saidbrush holder having a casing comprising an elongated spring, thecommutator end of said spring being attached to said casing and thedistal end of said spring terminating in a selfwinding volute, saidcasing having an opening therethrough with a reaction surface on theinside edge thereof, and a brush adapted to engage a commutator, theother end of said brush having means thereon to restrain said voluteagainst movement toward said reaction surface, said means comprising aplate attached to the end of said brush remote from said commutator andhaving a second plate attached to said first plate and extendinggenerally perpendicular thereto, said first plate overhanging the edgeof said brush adjacent said spring and having a concave surface thereon,said spring engaging said concave surface whereby said spring urges saidbrush toward said commutator and toward said reaction surface, saidbrush being offset from the center line of said commutator on the sidethereof toward said reaction surface, and a keeper extendingco-extensive with said spring and upwardly therefrom and terminating ina portion overlying the volute of said spring disposed thereon with aspacer between said spring and said keeper, said cornmutator adapted torotate in a direction to urge said brush toward said reaction surface.

15. In combination, a dynamo-electric machine having a commutator, abrush holder attached to said machine adjacent said commutator, saidbrush holder having a casing and an elongated spring attached to saidcasing, the commutator end of said spring being attached to said casingand the distal end of said spring terminating in a self-winding volute,said casing having an opening therethrough with a reaction surface onthe inside edge thereof, and a brush adapted to engage a commutator, theother end of said brush having means thereon to restrain said voluteagainst movement toward said reaction surface, said means comprising amember embedded in the outer end of said brush intermediate there ofwhereby said volute urges said brush toward said commutator and towardsaid reaction surface.

16. The combination recited in claim 15 wherein an auxiliary spring isattached to said brush casing and is generally coextensive with saidelongated spring and urges the volute end of said elongated spring andsaid brush toward said reaction surface.

17. The combination recited in claim- 15 wherein said member embedded inthe outer end of said brush comprises a pin having one end embedded insaid brush and the other end extending above the surface of said brush.

McDonald July 1, 1952 Welch Nov. 30, 1954

